System and method for flame stabilization and control

ABSTRACT

A system and method for providing continuous measurement and control of a combustion device by altering the fuel composition delivered thereto. The system includes devices for sensing combustion characteristics or other device characteristics, and controlling the performance of the combustion device based on the sensed information. Performance control occurs via addition of one or more additives to the fuel to adjust combustion characteristics. Via such sensing and performance control, consistent combustion device performance may be maintained, despite varying fuel characteristics. In one variation, -characteristics of the combustion device in operation, such as flame characteristics, are sensed and used to adjust fuel characteristics via iterative addition of one or more additives.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.11/033,180, filed Jan. 12, 2005, now U.S. Pat. No. 7,435,080, the entireoriginal contents of which are hereby incorporated by reference. Thepresent invention claims priority to Provisional Application Ser. No.60/535,716, filed Jan. 12, 2004, entitled “System and Method for FlameStabilization and Control,” which is hereby incorporated by reference.The present invention also claims priority to Provisional ApplicationSer. No. 60/634,286, filed Dec. 9, 2004, entitled “Dilution of GaseousFuels with Inert Gases to Maintain Constant Combustion Characteristics,”which is also hereby incorporated by reference.

BACKGROUND Field of the Invention

The invention relates generally to combustion-related devices, andspecifically to combustion-related devices that monitor and controlcombustion via control of one or more additives to a fuel feed.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 contains a block diagram of various computer system componentsfor use with an exemplary implementation of a control system for fuelfeed for a combustion device, in accordance with an embodiment of thepresent invention.

FIG. 2 illustrates an example of a system that determines combustionperformance directly, according to one embodiment of the invention.

FIG. 3 illustrates an example of a method for determining combustionperformance directly, according to one embodiment of the invention.

FIG. 4 illustrates an example of a system that determines combustionperformance indirectly, according to one embodiment of the invention.

FIG. 5 illustrates an example of a method for determining combustionperformance indirectly, according to one embodiment of the invention.

BRIEF DESCRIPTION OF EMBODIMENTS OF THE INVENTION Description ofEmbodiments of the Method and System

Embodiments of the present invention provide methods and systems forreal-time or near real-time sensing or otherwise determining combustionrelated information, such as fuel characteristics, combustioncharacteristics, or other device characteristics, and controlling theperformance of a combustion device (e.g., a turbine or other devicecontaining a combustor), based on the sensed information, using anadditive to the fuel to adjust one or more combustion characteristics.Via such sensing and performance control, for example, consistentcombustion device performance may be maintained, despite varying inputsor other factors, such as varying fuel quality or type. Such variationsin fuel may include, for example, variations in combustioncharacteristics for natural gas, depending on the source of the naturalgas, or variations in fuel type to be used for the combustion device.

In a first embodiment, combustion device performance is controlled(indirectly) via sensing of fuel characteristics and addition of one ormore additives to the fuel feed, as necessary. For example, in onevariation of this embodiment, fuel characteristics (e.g., fuel feed rateand chemical or other aspects of the fuel relating to combustionperformance of the fuel) for the fuel to be fed to the combustion deviceare monitored, such as via fuel composition and feed rate sensors. Themonitored results are compared to an acceptable range of fuelcharacteristics (e.g., a range of fuel characteristics that produceacceptable combustor performance), and if the monitored results areoutside the acceptable range, an appropriate amount of an available fueladditive is determined, and the additive is added to the fuel feed, soas to produce combustor performance that would have resulted had thefuel been within the acceptable range.

For example, if the fuel without additive is determined by analysis ofthe fuel to produce too slow of a flame speed within the combustor, anappropriate calculated amount of combustion enhancer (based, forexample, on calculated combustion enhancement with the additive, giventhe sensed rate of fuel feed) as an additive is added to the fuel feed,so as to increase the flame speed to an acceptable level. On the otherhand, if the fuel without additive is determined by analysis of the fuelto produce too fast of a flame speed within the combustor, anappropriate calculated amount of combustion retardant as an additive isadded to the fuel feed, so as to decrease the flame speed to anacceptable level. In this embodiment, once the proper additivecharacteristics for the fuel are determined, no continuous additionalmonitoring and control is necessary (although additional monitoring andcontrol may optionally be used, either at the fuel or combustion end ofthe combustion device, so as, for example, to maintain combustionquality).

In a second embodiment, combustion device performance is controlled viasensing of combustor performance characteristics, with addition of oneor more additives to the fuel feed being provided, as necessary, toplace the combustor within an acceptable performance range. For example,in one variation of this embodiment, combustion performancecharacteristics (e.g., pressure produced in the combustor, combustion oremission products, temperature, or other combustion features) aremonitored, and the monitored results are compared to an acceptable rangeof combustion performance characteristics (e.g., a range of combustioncharacteristics that produce acceptable combustor performance). If themonitored results are outside the acceptable range, an appropriateamount of an available fuel additive is added to the fuel feed, andcombustor characteristics are remonitored to determine if the resultsare within the acceptable range. This process is repeated, as acontinuous feedback loop, until the combustion characteristics fallwithin an acceptable range, and additive feed is then maintained.

For example, if the fuel without additive is determined by combustorperformance characteristics to produce too low of a flame temperaturewithin the combustor, a feed of a combustion enhancer as an additive isadded to the fuel feed, so as to produce an increase in the flametemperature. If an acceptable flame temperature is reached, the feed ofadditive is maintained; otherwise, more additive is iteratively addeduntil an acceptable flame temperature is reached. Similarly, if the fuelwithout additive is determined by combustor performance characteristicsto produce too high of a flame temperature within the combustor, a feedof a combustion retardant as an additive is added to the fuel feed, soas to produce a decrease in the flame temperature. If an acceptableflame temperature is reached, the feed of additive is maintained,otherwise, more additive is iteratively added until an acceptable flametemperature is reached.

In an exemplary second variation of the second embodiment, other(non-combustion) characteristics of the combustion device are monitoredto determine performance, and additive is added, as necessary, so as toplace or maintain the combustion device within an acceptable performancerange. For example, vibration in the combustion device may result ifpressure fluctuations within the combustor are too high. Similarly tothe first variation for this embodiment, an additive to produce anincrease in pressure in the combustor is iteratively added to the fuelfeed until acceptable performance (e.g., acceptable vibration level) isproduced for the combustion device.

In each variation of the second embodiment, sensed fuel feed rates andfuel characteristics or other information may be used in conjunctionwith the sensed combustion device characteristics so as, for example, tomore precisely determine and control additive feed.

In order to carry out these functions with a combustion device, each ofthe embodiments of the present invention generally utilize one or moresensors, one or more sources of additives, one or more additive flowcontrol devices (e.g., valves) having one or more corresponding controlmechanisms, and one or more processors or processing devices to receivethe sensor input, to optionally determine appropriate amounts ofadditive to add to the fuel flow (depending on the embodiment), and todirect the operation of the additive flow control devices via thecontrol mechanisms.

Combustion Device. The combustion device usable with the presentinvention may comprise any a number of known or developed combustor orburner devices used to combust fuel and that may be used for any numberof purposes that such devices are typically used. For example, thecombustion device may comprise a turbine or reciprocating enginedesigned to use natural gas or other fuel (or, for example, capable ofrunning on, or being adjusted to run on, a variety of fuels) for powergeneration.

Sensors. A wide number of sensors are usable with the present invention.For example, such sensors usable with the present invention can directlyor indirectly measure fuel composition, or combustion properties, orboth. When directly measuring fuel composition, a number of techniquescan be utilized within the sensors (or, for example within theprocessors or processing devices coupled to the sensors, as describedfurther below) to measure the amounts of the various chemical speciesthat make up the fuel. These techniques include, but are not limited to:infrared absorption spectroscopy; Fourier Transform Infra-Red (FTIR)spectroscopy; Raman spectroscopy; gas chromatography; mass spectrometry;nuclear magnetic resonance; electron spin resonance; or ion mobilityspectroscopy; or any combination thereof.

When indirectly measuring fuel composition, the procedures that can beutilized include, but are not limited to, the following: use of flameionization detectors (FID); thermal conductivity measurement; heatcapacity measurement; speed of sound measurement; or densitymeasurement; or any combination thereof. Particularly when used withembodiments involving indirect measurement, the sensors can also measureor be used to determine indices of combustion performance, as necessary,including a Wobbe Index, as described in detail below, and the sensorscan include known types and methods designed to measure flow rate forthe fuel.

With regard to flame sensing (direct measurement), sensors can be usedto measure combustion stability by, for example, measuring flamelocation or oscillation or both utilizing (but not limited to) one ormore of the following: a chemiluminescence detector; a flame scanner; aflame imager; or a flame detector. The sensors can also be selected orconfigured to measure combustion stability by measuring, for example,combustion chamber pressure and pressure fluctuations, or anaccelerometer may be used to measure vibrations in the combustion deviceresulting from combustion induced pressure oscillations. Combustionperformance can be measured by measuring such characteristics ascombustion flame temperature; exhaust temperature; or emissions; or anycombination thereof.

Processor. The processor (also interchangeably referred to herein as a“processing device” or “controller”) can perform calculations to assesscombustion performance or stability based on inputs from the sensors orother information, and is capable of generating control signals,mechanical or hydraulic operations, or other control functions for theadditive system (e.g., to control valves or other mechanisms to controladditive feed), such that constant combustion performance and/orstability is produced and maintained. The controller can control theproperties of the input fuel to the combustor (e.g., by controlling feedof one or more additives), such that, for example, both constant heatrate and fuel jet characteristics can be maintained. The controller canalso maintain constant combustion properties by such methods asmaintaining a constant index of combustion. The index, as describedbelow, can be a Wobbe Index, or a Weaver Index, or both (or some otherindex devised to characterize combustion properties of a fuel).

The controller can also maintain stable combustion by, for example,adjusting flame speed or some other primary combustion property (e.g.,through control of the amount of additive added to the fuel). Thecontroller can be an analog device, such as a PID (Proportional,Integral, Derivative) controller generating the control output from theinput signal through the use of tuned control coefficients. Thecontroller can also be a digital device, such as a PLC (ProgrammableLogic Controller) or computer. A computer can mimic an analog device insoftware, or it can use the information from the sensing system tocalculate a combustion index or other fuel property and then calculatethe required additive level to maintain a predetermined value of theindex or property. The controller may be a stand-alone device, or maycomprise more than one coupled device, including devices forming orcoupled to a network, such as the Internet. Such a device or devices mayhave a “learning” capability, which allows the invention toself-optimize the controlling algorithms based on operationalexperience, as applicable for some embodiments.

Output of the controller may also be correlated with combustion devicestability and used as a stability indicator. The stability indicator maybe used to shut down the combustion device before a severe loss ofstability occurs. In addition, the stability indicator may be used aspart of or in conjunction with other features for a combustion device,such as to develop an operating record to aid in determining the causeof upsets.

As shown in FIG. 1, the controller of the present invention may beimplemented using hardware, software or a combination thereof and may beimplemented in one or more computer systems or other processing systems.In one embodiment, the invention is directed toward one or more computersystems capable of carrying out the functionality described herein.

Computer system 1 includes one or more processors, such as processor 4.The processor 4 is connected to a communication infrastructure 6 (e.g.,a communications bus, cross-over bar, or network). Various softwareembodiments are described in terms of this exemplary computer system.After reading this description, it will become apparent to a personskilled in the relevant art(s) how to implement the invention usingother computer systems and/or architectures.

Computer system 1 can include a display interface 2 that forwardsgraphics, text, and other data from the communication infrastructure 6(or from a frame buffer not shown) for display on the display unit 30.Computer system 1 also includes a main memory 8, preferably randomaccess memory (RAM), and may also include a secondary memory 10. Thesecondary memory 10 may include, for example, a hard disk drive 12and/or a removable storage drive 14, representing a floppy disk drive, amagnetic tape drive, an optical disk drive, etc. The removable storagedrive 14 reads from and/or writes to a removable storage unit 18 in awell known manner. Removable storage unit 18, represents a floppy disk,magnetic tape, optical disk, etc., which is read by and written toremovable storage drive 14. As will be appreciated, the removablestorage unit 18 includes a computer usable storage medium having storedtherein computer software and/or data.

In alternative embodiments, secondary memory 10 may include othersimilar devices for allowing computer programs or other instructions tobe loaded into computer system 1. Such devices may include, for example,a removable storage unit 22 and an interface 20. Examples of such mayinclude a program cartridge and cartridge interface (such as that foundin video game devices), a removable memory chip (such as an erasableprogrammable read only memory (EPROM), or programmable read only memory(PROM)) and associated socket, and other removable storage units 22 andinterfaces 20, which allow software and data to be transferred from theremovable storage unit 22 to computer system 1.

Computer system 1 may also include a communications interface 24.Communications interface 24 allows software and data to be transferredbetween computer system 1 and external devices. Examples ofcommunications interface 24 may include a modem, a network interface(such as an Ethernet card), a communications port, a Personal ComputerMemory Card International Association (PCMCIA) slot and card, etc.Software and data transferred via communications interface 24 are in theform of signals 28, which may be electronic, electromagnetic, optical orother signals capable of being received by communications interface 24.These signals 28 are provided to communications interface 24 via acommunications path (e.g., channel) 26. This path 26 carries signals 28and may be implemented using wire or cable, fiber optics, a telephoneline, a cellular link, a radio frequency (RF) link and/or othercommunications channels. In this document, the terms “computer programmedium” and “computer usable medium” are used to refer generally tomedia such as a removable storage drive 14, a hard disk installed inhard disk drive 12, and signals 28. These computer program productsprovide software to the computer system 1. The invention is directed tosuch computer program products.

Computer programs (also referred to as computer control logic) arestored in main memory 8 and/or secondary memory 10. Computer programsmay also be received via communications interface 24. Such computerprograms, when executed, enable the computer system 1 to perform thefeatures of the present invention, as discussed herein. In particular,the computer programs, when executed, enable the processor 4 to performthe features of the present invention. Accordingly, such computerprograms represent controllers of the computer system 1.

In an embodiment where the invention is implemented using software, thesoftware may be stored in a computer program product and loaded intocomputer system 1 using removable storage drive 14, hard drive 12, orcommunications interface 24. The control logic (software), when executedby the processor 4, causes the processor 4 to perform the functions ofthe invention as described herein. In another embodiment, the inventionis implemented primarily in hardware using, for example, hardwarecomponents, such as application specific integrated circuits (ASDICS).Implementation of the hardware state machine so as to perform thefunctions described herein will be apparent to persons skilled in therelevant art(s).

In yet another embodiment, the invention is implemented using acombination of both hardware and software.

Additive Feed. The additive feed portion of the present inventionprovides capability to add the additives to the fuel, as appropriate,per the controller calculations or other controller function. Theadditive feed portion of the present invention can include, but does notrequire, a reservoir for holding additives. The additive portion of thepresent invention can also add additives “on the fly” by using readilyavailable material, such as steam, air, readily available exhaust gases,or other generated or genera table material. Such additives can begenerated, for example, by taking a component (e.g., air or water) andseparating it into one or more components to be used with the presentinvention, or by generating a reaction to a particular component.

Such additives can derived, for example, from exhaust gases or via useof air separation methods, and can also include or use of steam orwater. In addition, the additives in the additive system can comprisereactive chemical species, which act, for example, as combustionenhancer, including, but not limited to: hydrogen (H2); acetylene(C2H2); nitrous oxide (N2O); or any combination thereof. To function ascombustion retardants, the additives can comprise inert diluents,including, but not limited to: nitrogen (N2); air; oxygen depleted air;carbon dioxide (CO2); recirculated exhaust gas; water; or steam; or anycombination thereof. Combustion retardant additives can also similarlycomprise flame retarding species, including, but not limited to halogencontaining species.

The additive feed portion of the present invention can comprise meteringvalves or other valves or control mechanisms to control how muchadditive is mixed with the fuel, as well as electronic, mechanical,hydraulic, or other operating mechanisms to control operation of thecontrol mechanisms. The metering valves, either directly or through suchcontrol mechanism or mechanisms, can be controlled, for example, viacoupling to the controller.

Properties of Fuel and Combustion Devices

The following fuel and combustion device information and properties aregenerally applicable to systems and methods for implementing embodimentsof the present invention.

Fuel Characteristics. Certain fuel characteristics help determinewhether different fuels will behave similarly in the same combustiondevice. If a parameter known as the Wobbe Index is the same for bothfuels, they will often behave similarly in a given combustion system. AWobbe Index (WI) is defined as the ratio of the volumetric calorificvalue of the fuel to the square-root of the fuel density. When the WI isthe same for two fuels, heat input to the device for the two fuels willbe approximately equal, with same pressure drop across the fuel inletnozzles. Fuel jet penetration and thus fuel-air mixing will also beapproximately the same. Thus, maintaining a constant fuel WI isimportant to maintaining constant performance of a combustion device.

The WI was originally developed to determine the interchangeability offuels burned in diffusion flame combustors and simple premixed burnersthat operate in a stable combustion regime, for which constant heat rateis a suitable constraint on gas interchangeability. Lean, premixed DryLow Emissions (DLE) combustors (such as those used in modern gasturbines used for power generation), however, operate in a less stablecombustion regime, so heat rate alone is typically not a sufficientconstraint to guarantee consistent operation. Thus, application of theWI for computing interchangeability in lean-premixed combustors may notalways be sufficient, without consideration of further constraints.Other indices have been developed that monitor for interchangeability ofother flame properties. For example, the Weaver Index compares the heatrelease, flame lift, flashback, and yellow tipping of a proposedsubstitute gas, relative to a reference gas, for a combustionapplication. In addition, fundamental combustion properties, such asflame speed, may also be monitored for use as part of a method topredict combustion stability.

Combustion stability control may thus be achieved by adjusting thechemical composition of the fuel mixture entering the combustor, so thatfuel characteristics, like those described above, are controlled. Thismay be accomplished by changing the fuel stream composition through theaddition of additives to the fuel mixture. Additives can increase ordecrease flame speed, flame temperature, or volumetric heat releaserate, for example. Additives include, but are not limited to: reactivechemical species (e.g., hydrogen, acetylene, or N2O); diluents (e.g.,nitrogen, CO2, steam, or recirculated exhaust gases); or flame-radicalscavenging chemical species (e.g., halogen containing species); or anycombination thereof.

Premixed Combustion Devices and Burners. Premixed combustion devicesusable with the present invention can include, but are not limited to,those used in low-emissions gas turbines, for which operation may sufferin the face of variable natural gas or other feed gas (such as processgas or syngas) composition. Premixed combustion systems that are tunedfor very low pollutant emissions operate in a narrow stability regionbetween flashback and blow-off. Flashback occurs when the flame speed isfaster than the flow velocity through the combustor, allowing flamepropagation upstream. Blow-off occurs when the flame speed is slowerthan the flow velocity through the combustor, allowing the flame to beblown downstream and extinguished. Flame speed must generally equal flowvelocity for stable combustion. Numerous techniques are used tostabilize the flame so that flame speed does not have to exactly matchflow velocity.

These constraints result in a small window of stability; however, toogreat a mismatch between flame speed and flow velocity can still resultin flashback or blow-off. Since flame speed is a function of fuelcomposition, stability problems can arise due to the variablecomposition of natural gas or other feed gases (see, e.g., “Influence ofVariations in the Natural Gas Properties on the Combustion Process inTerms of Emissions and Pulsations for a Heavy Duty Gas Turbine” by L.Nord and H. Andersen, the contents of which are hereby incorporated byreference in their entirety). Premixed combustors are particularlysensitive to variability of fuel properties, as the premixing dependscritically on control of the fluid mechanics, and flame stability isdependent on fluid mechanics and chemical kinetics. The loss of flamestability leads to pressure fluctuations and pulsations, and resonantacoustics, which can cause damage to and degradation of hot sectioncomponents. (These characteristics, however, also may be sensed orotherwise utilized to assist with operation of the combustion device, inaccordance with some embodiments of the present invention.)

Example Embodiments

Combustor performance may be measured and/or sensed in numerous ways.For example, combustor performance may be measured and/or senseddirectly by determining performance characteristics of the combustiondevice, or performance may be measured and/or sensed indirectly bydetermining fuel characteristics. In both of these examples, theaddition of additives (e.g., reactive species, reaction inhibitingspecies, or inert diluents) to the fuel can be used to cause a change inthe fuel composition. The direct measurement may be used as the input ina feedback type control loop, while the indirect measurement may be usedas the input in a feed-forward type control loop.

Combustion performance may be determined directly by determiningperformance characteristics of a combustion device. For example,stability can be determined by measuring an indicator of flame positionin the combustor, such as flame chemiluminescence, or by sensing flameintermittency by detecting, for example, the acoustic or optical(chemiluminescence) emissions generated by the flame. FIG. 2 illustratesan example of a system that determines combustion performance directly,according to one embodiment of the invention. As illustrated in FIG. 2,the system comprises: a fuel line 105; a sensing system 110; acontroller 115 to access the information from the sensing system 110(e.g., to control the fuel composition or provide a stability riskassessment, data records, and emissions predictions); an additive system120 to control the fuel additive(s) using the information provided bythe controller 115; and a combustor 125 to burn the fuel.

FIG. 3 illustrates an example of a method that determines combustionperformance directly, according to one embodiment of the invention. Instep 205, at least one combustion characteristic is determined using thesensing system. For example, a flame or combustor characteristic such asdynamic pressure oscillations could be measured. These dynamic pressureoscillations could be measured using a pressure transducer thatindicates changes in combustor pressure as a function of time. In step210, the controller analyzes the combustion characteristic(s). Thus, forexample, the dynamic pressure oscillations could be analyzed todetermine a running average or be compared to prescribed limit values.If the analysis indicates that the combustor performance isdeteriorating, some change to fuel composition may be needed. In step215, the output from the controller determines if the fuel compositionshould be changed to correct a combustion dynamics problem. If noproblem is indicated (e.g., fuel composition is within predeterminedacceptable range for combustion device operation), in step 220, the datacan be archived, and the system can continue to be monitored. If thereis a problem (e.g., fuel composition is outside of predeterminedacceptable range for combustion device operation), in step 225, theproper change to the fuel composition (e.g., addition of appropriateadditive to fuel feed) is determined. The change to the fuel compositioncan be determined from, for example, prior experience with a particularcombustion system, from computation of a stability index or fundamentalflame property, or by other information or method. In step 230, a signalis sent to the additive system indicating that a certain amount ofadditive should be mixed into the fuel stream. In step 235, the fuelentering the combustor is modified accordingly (e.g., by causing theopening or adjusting of a valve). Thus, in the example, the fuelentering the combustor is modified by the addition of the additive tohave combustion characteristics that produce a more stable flame. Thesesteps comprise a feedback control loop that may require iteration orother techniques to optimize the additive process.

Combustion performance may also be determined indirectly by measuringfuel characteristics (e.g., chemical composition, density and heatingvalue) and inferring combustion behavior. FIG. 4 illustrates an exampleof a system that determines combustion performance indirectly, accordingto one embodiment of the invention.

As illustrated in FIG. 4, the system comprises: a fuel line 305; acombustor 325 to burn the fuel; a sensing system 310; a controller 315to access the information from the sensing system and determine how muchfuel additive(s) to add or otherwise select to vary the additive(s)delivered to the fuel; and an additive system 320 to store and controlthe flow of the additive(s) into the fuel line.

FIG. 5 illustrates an example of a method that determines combustionperformance indirectly, according to one embodiment of the invention. Instep 405, the sensing system determines the fuel characteristics. Thus,for example, the sensing system can utilize an FTIR spectrometer tomeasure the individual chemical species that make up the fuel. In step410, the controller analyzes the fuel characteristics. Thus, forexample, the controller utilizes the fuel composition to compute aregulating quantity, such as the flame speed, and/or Wobbe Index oranother stability index. In step 415, the output from the controller isanalyzed to determine if the fuel composition should be changed to meetthis goal (e.g., to fall within a predetermined range). Thus, forexample, if the composition of the fuel is changing, such that theregulating quantity indicates a flame stability problem, the compositioncan be altered before combustion problems arise. If the value of theregulating quantity does not need to be changed, in step 420 the datacan be archived, and the regulating quantity can continue to bemonitored. If value of the regulating quantity does need to be changed,in step 425, a determination is made that changes need to be made. Thechanges to fuel composition required to alter the value of theregulating quantity may require addition of a diluent or reactivespecies to obtain the necessary alteration of combustioncharacteristics. In step 430, the proper change to the fuel compositionis determined. Thus, for example, the adjustment required to the fuelcomposition to maintain flame stability and/or pollutant emissions isdetermined. In step 435, a signal is sent to the additive system 320controlling the amount of either diluent or reactive species to be mixedinto the fuel stream to obtain the required composition and hence valueof regulating quantity. In step 440, the fuel entering the combustor ismodified accordingly thus improving the flame stability characteristicsin order to minimize pressure oscillations in the combustor.

Example Applications and Other Uses of Information Generated. Asexplained above, embodiments of the present invention can be used tostabilize a combustion system (in both premixed and non-premixedcombustors), to thereby compensate for effects of time-varying fuelcomposition and combustion properties. In addition, the measurement ofinput fuel composition may also be useful. For example, emissionspredictions (e.g., predicting the emissions level based on the measuredchemical composition of the fuel), stability risk assessments (e.g.,blow-off or flashback due to a measured chemical composition), andarchival records, from which the cause of combustor upsets may bedetermined, can be utilized. Another application is to use thecomposition and/or flame speed information to perform a continuousassessment of the risk of loss of combustor stability. Furthermore, fuelcomposition information can be used to augment calculation of combustiondevice NOx emissions based on combustion device operating parameters.One embodiment could also be used with a surrogate combustor or burnerfor the purpose of adjusting the composition of the fuel supply to anumber of combustion devices that obtain fuel from the source withoutthe need to monitor the other combustion devices. Another embodimentcould be used to control individual combustion devices by customizingthe fuel sent to each combustion device. Those experienced in the artwill realize that the above uses are merely examples, and that multipleother uses are possible.

The present invention is described in terms of the above embodiments.This is for convenience only and is not intended to limit theapplication of the present invention. In fact, after reading thedescription of the present invention, it will be apparent to one skilledin the relevant arts how to implement the present invention inalternative embodiments.

In addition, it should be understood that the Figures described above,which highlight the functionality and advantages of the presentinvention, are presented for example purposes only. The architecture ofthe present invention is sufficiently flexible and configurable, suchthat it may be utilized in ways other than that shown in the Figures.

Further, the purpose of the Abstract of the Disclosure is to enable theU.S. Patent and Trademark Office and the public generally, andespecially the scientists, engineers and practitioners in the art whoare not familiar with patent or legal terms or phraseology, to determinequickly from a cursory inspection the nature and essence of thetechnical disclosure of the application. The Abstract of the Disclosureis not intended to be limiting as to the scope of the present inventionin any way.

1. A fuel feed adjustment system for use with a combustion device havinga gaseous fuel feed, the system comprising: a sensor for sensing acombustion characteristic for the combustion device; a processor forcomparing the sensed combustion characteristic to an acceptable rangeand for outputting an output when the sensed combustion characteristicis outside the acceptable range; and an additive feed for feeding anadditive to the fuel feed, the additive feed being triggered by theoutput.
 2. The system of claim 1, wherein the combustion characteristicfor the combustion device comprises a flame characteristic.
 3. Thesystem of claim 2, wherein the flame characteristic comprises at leastone of: flame flicker; flame color; flame products composition; flamelocation; or flame oscillation; or any combination thereof.
 4. Thesystem of claim 2, wherein the sensor comprises at least one of: achemiluminescence detector; a flame scanner; an accelerometer; a flameimager; a pressure transducer; a sound sensor; a motion sensor; or aflame detector; or any combination thereof.
 5. The system of claim 1,wherein the sensor determines combustion stability or combustionperformance or both.
 6. The system of claim 5, wherein combustionstability is determined by measuring chamber pressure or chamberpressure fluctuation or both.
 7. The system of claim 5, whereincombustor performance is determined by measuring at least one of flametemperature; exhaust temperature; emissions content; or any combinationthereof.
 8. The system of claim 1, wherein the sensor comprises at leastone of: a pressure transducer; a sound sensor; a vibration sensor; or amotion sensor; or any combination thereof.
 9. The system of claim 1,wherein the combustion device is a turbine.
 10. The system of claim 1,wherein the combustion device is a reciprocating engine.
 11. The systemof claim 1, wherein the fuel feed is a natural gas feed.
 12. The systemof claim 1, wherein the additive feed is provided from an additive feedsource.
 13. The system of claim 12, wherein the additive feed iscontrolled via a feed control mechanism.
 14. The system of claim 13,wherein the feed control mechanism comprises a metering valve.
 15. Thesystem of claim 1, wherein the processing device comprises an analogcontroller or a digital computer or both.
 16. The system of claim 1,wherein the sensed combustion characteristic is used to control feedingof a second additive feed to the fuel feed for a second combustiondevice.
 17. The system of claim 1, wherein the fuel feed with the fedadditive is connected to a second combustion device.
 18. A fuel feedadjustment system for use with a combustion device having a gaseous fuelfeed, the system comprising: a sensor for sensing a combustioncharacteristic for the combustion device; a processor for comparing thesensed combustion characteristic for the combustion device to anacceptable range and for producing a first output upon the sensedcombustion characteristic being outside the acceptable range and asecond output upon the sensed combustion characteristic being within theacceptable range; and an additive feed for feeding an additive to thefuel feed, the additive feed being triggered by the first output, andtermination of the additive feed being triggered by the second output.19. A method for adjusting a gaseous fuel feed for a combustion device,the method comprising: sensing a combustion characteristic for thecombustion device; comparing the sensed combustion characteristic to anacceptable range to produce a comparison result; and variably feeding anadditive to the fuel feed depending on the comparison result.